Over the past few years, 4D flow MRI has become a hot topic in basic and clinical research. This phase contrast imaging technique provides the unique opportunity to measure three-dimensional blood flow velocities in the heart and adjacent large vessels throughout a cardiac cycle (three spatial dimensions over time, thus 4D flow).

Interesting 4D flow applications have emerged for the aorta and pulmonary artery, including measurement of blood flow, estimation of pressure gradients and pressures, and calculation of vessel wall shear stress and pulse wave velocities. Furthermore, 4D flow enables visualisation of the complex three-dimensional blood flow patterns in the cardiac chambers, as well as computation of novel velocity-derived parameters like blood vorticity and kinetic energy.

For the left ventricle, there is a lot of hope for 4D flow to provide information about diastolic function, a diagnostic aspect where MRI is currently inferior to the gold standard technique of echocardiography. Preliminary studies have shown good agreement of early and late diastolic left ventricular inflow velocities measured with 4D flow and echocardiography, respectively. Moreover, new metrics of diastolic function are expected to emerge from analysis of information contained in intraventricular blood flow patterns.

One prominent left ventricular blood flow pattern is the mitral valve vortex ring, a three-dimensional swirling blood flow structure that forms at the mitral valve leaflets during diastole in healthy as well as diseased subjects. While the mitral valve vortex ring is assumed to support ventricular filling, to store kinetic energy of blood entering the left ventricle, and to help redirect mitral inflow towards the aorta, studies also suggest that properties of the mitral valve vortex ring may be altered in left ventricular diastolic dysfunction. More studies are needed to fully understand the meaning of the mitral valve vortex ring; however, its analysis is challenging due to the complexity of vortex structures, which is why most existing vortex ring evaluation techniques rely on visual inspection or manual vortex delineation.

Streamline visualisation of an early diastolic mitral valve vortex ring from different perspectives.

The cardiac MRI group at the Medical University of Graz, Austria, has developed prototype software for automated detection and analysis of the mitral valve vortex ring from 4D flow MRI data. The algorithm automatically extracts the temporal evolution of the mitral valve vortex ring and calculates velocity-derived and vortex ring shape parameters.

In our study, the mitral valve vortex ring extraction software was used for analysis of the relationship of vortex ring kinetic energy with systolic and diastolic left ventricular function parameters in 21 healthy subjects. In today’s presentation, we will show that early and late diastolic peak vortex ring kinetic energies are strongly correlated with early and late diastolic left ventricular inflow velocities, which suggests the mitral valve vortex ring as an important structure for studying and understanding left ventricular diastolic function.

Corina Kräuter, MSc, is a PhD student at the Institute of Medical Engineering, Graz University of Technology, Austria, and a Research Assistant at the Department of Radiology, Medical University of Graz, Austria.

Research Presentation Session
RPS 703 Cardiac function: advanced imaging techniques

4D-flow-derived mitral valve vortex ring: the relationship with left ventricular functio
C. Kräuter1, U. Reiter1, C. Reiter1, V. Nizhnikava1, M. Masana2, A. Schmidt1, M. Fuchsjäger1, R. Stollberger1, G. Reiter1; 1Graz/AT, 2Barcelona/ES

Read the full abstract in the ECR 2020 Book of Abstracts
Kräuter C, et al. (2020) 4D-flow-derived mitral valve vortex ring: the relationship with left ventricular function. Abstract RPS 703-1 in: ECR 2020 Book of Abstracts. Insights Imaging 11, 34 (2020). DOI 10.1186/s13244-020-00851-0